1. Field of Use
The present invention relates to positioning apparatus and more particularly to base support apparatus for adjusting the degree of tilt of the screen of a cathode ray tube display terminal device.
2. Prior Art
There has been a significant increase in the frequency of use of cathode ray tube (CRT) display terminal devices. Therefore, it becomes more esential to make such devices more convenient and comfortable for an operator to use.
One problem encountered by operators concerns the amount and angle of incident light which falls on the screen surface of the CRT display device and produces reflections making it impossible in some instances for an operator to view information being displayed on the screen. Normally, the amount of incident light varies with the time of day and the placement or positioning of the CRT device on the operator's work space. In view of this, it becomes very desirable for an operator to be able to alter the viewing angle of the CRT's screen surface so as to minimize or eliminate reflections.
Some prior art CRT display devices have the tilt mechanism built into the device. That is, the CRT tube casing or housing is mounted on pivotal support base structures which permit the tube screen to be tilted by the operator.
This type of arrangement has been found to introduce additional problems in constructing a suitable plastic housing or casing structure for the device. Also, it becomes difficult to provide a tilt mechanism sturdy enough to meet stringent shock and vibration test requirements.
Another prior art CRT display device uses a chassis which is pivotally mounted on a frame by two pivot pins. The viewing angle is adjusted by pivoting the chassis about the pivot pins. An example of this type of arrangment is disclosed in IBM Technical Disclosure Bulletin "Adjustable Mount for CRT Terminal", Vol. 21, No. 3, August 1978. These types of arrangements also have been found to require complex construction which results in increase in costs.
To reduce costs, other prior art arrangements have utilized free standing tilt mechanisms. One such unit is described in U.S. Pat. No. 4,368,867. Another such unit has a three piece construction which includes a base plate, a top plate and an adjustable flap. The flap is hinged to the base plate and can be latched into a series of slots on the top plate by means of a spring biased arrangement.
The first arrangement has the disadvantage of requiring some amount of assembly prior to use with a CRT terminal unit. The second arrangement requires that the top plate on which the CRT terminal unit rests must be lifted by an operator and the flap latched into the desired slot. This has been found to introduce difficulties in operator adjustments.
Accordingly, it is a primary object of the present invention to provide CRT terminal base support for adjustment of the CRT screen viewing angle which is inexpensive to construct.
It is a further object of the present invention to provide a tiltable base support which provides a wide range of CRT screen viewing angle adjustment without requiring two hands.